Male hedgehog or female hedgehog?
There are two species of sea urchin best known to us: the Paracentrotus lividus, known as purple hedgehog or female hedgehogwhich is commonly found in the rocky bottoms populated by algae and by the prairies of Poseidonia and within 10 - 15 cm of depth, and the hedgehog Arbacia lixula commonly said black hedgehog or male hedgehog deemed inedible.
In fact, the two species are distinguished from each other by the color: one black-horny, the other brown-brown.
The Paracentrotus lividus it is found in the cliffs within niches specially dug by means of the teeth that make up the so-called "Aristotle's lantern" which is nothing more than the chewing mouth apparatus of this organism. This species also does not like the light and in fact during the day they find themselves covered with pebbles, shells, algae, etc. During the night, however, they become active and move in search of food mainly represented by vegetables even if they do not disdain small animals such as sponges, hydrozoans or the remains of other organisms.
If you would like more information on the subject, consult the technical sheet: Sea urchins